Planetary Boundaries

Two major studies by an international team of researchers, published in Science and Anthropocene Review last year, pinpointed the key factors that ensure a habitable planet for humans and found that of these nine world wide processes, four have already exceeded safe levels. These processes are referred to as Planetary Boundaries and the four critical ones are:

  • Climate change
  • Loss of biosphere integrity (biodiversity loss and extinctions)
  • Land system change
  • Nitrogen and phosphorus flows to the biosphere and oceans

All of these changes are shifting Earth into a new state that is becoming less hospitable to human life and these changes are down to human activity, not natural variability. Our economic systems have gone into overdrive and as a result there has been a massive increase in resource use and pollution on a global scale.

Climate Change

Mark Maslin, in his column in Geographical magazine, points out that…

“…humans have increased atmospheric CO2 by 40 per cent, up to a level not seen for at least the last million years, increasing the acidity of the ocean at a faster rate than is estimated to have occurred at any time in the last 50 million years. The increased levels of greenhouse gases have elevated global temperatures by over 0.85°C and raised the worldwide average sea-level by over 20cm. Far worse is expected by the end of the century.”

Since 1950, urban populations have increased seven-fold and primary energy use has soared by a factor of five. Carbon dioxide levels have now breached 400 parts per million for the first time in history.

Will Seffen, lead author on the two studies into Planetary Boundaries, believes we’ve reached a point at which the loss of summer polar sea-ice is almost certainly irreversible.

“This is one example of a well-defined threshold above which rapid physical feedback mechanisms can drive the Earth system into a much warmer state with sea levels metres higher than present.”

He also suggests that the weakening or reversal of carbon sinks (a forest, ocean, or other natural environment viewed in terms of its ability to absorb carbon dioxide from the atmosphere), such as the on-going destruction of the world’s rain forests, is another potential tipping point, where feedbacks accelerate Earth’s warming and this intensifies the climate impacts.

“A major question is how long we can remain over this boundary before large, irreversible changes become unavoidable.”


Loss of biosphere integrity (biodiversity loss and extinctions)

This is the second of the 4 critical planetary boundaries; another problem which is spiralling out of control, with species now becoming extinct at a rate more than 1000 times faster than the previous norm.

The study of Planetary Boundaries concludes that changes to ecosystems due to human activities have been…

“… more rapid in the past 50 years than at any time in human history, increasing the risks of abrupt and irreversible changes. The main drivers of change are the demand for food, water, and natural resources, causing severe biodiversity loss and leading to changes in ecosystem services.”

A study last year by scientists at WWF and the Zoological Society of London found that the number of wild animals on Earth has halved in the past 40 yearsCreatures across land, rivers and the seas are being decimated as humans kill them for food in unsustainable numbers, while polluting or destroying their habitats.

We are destroying natural habitats at an alarming rate, and this ecosystem damage, alongside the illegal wildlife trade, is leading to extinctions which will ultimately destroy the integrity our living global ecosystem (what scientists refer to as the biosphere). Steffen believes that direct human influence upon the land is contributing to a loss of pollination and a disruption of nutrients and fresh water.

We are clearing land, we are degrading land, we introduce feral animals and take the top predators out, we change the marine ecosystem by overfishing – it’s a death by a thousand cuts”

Land system change

Land is converted to human use all over the planet. Forests, grasslands, wetlands and other vegetation types have been converted to agricultural land. This land-use change is one driving force behind the serious reductions in biodiversity, and it has impacts on water flows and on the absorption of carbon, nitrogen and phosphorus, showing how interconnected these processes are. The study of Planetary Boundaries tells us:

“While each incident of land cover change occurs on a local scale, the aggregated impacts can have consequences for Earth system processes on a global scale…. Forests play a particularly important role in controlling the linked dynamics of land use and climate.”

Land clearing is now concentrated in tropical areas, such as Indonesia and the Amazon, with the practice reversed in parts of Europe. But the overall picture is one of deterioration at a rapid rate.

That direct impact upon the land is the most important factor right now, even more than climate change.” – Will Steffen

Nitrogen and phosphorus flows to the biosphere and oceans

This final process refers to the high level of phosphorus and nitrogen flowing into the oceans due to fertilizer use. This is now eight times higher than in 1950.

Mark Maslin, writing in Geographical summarises as follows:

“In the early 20th century, the invention of the Haber-Bosch process – allowing the conversion of atmospheric nitrogen to ammonia for use as fertiliser – altered the global nitrogen cycle so radically that the nearest suggested comparison occurred over two billion years ago.”

Much of the nitrogen in fertilizers is emitted to the atmosphere in various forms rather than taken up by crops. Then, when it rains, it pollutes waterways and coastal zones and accumulates in our oceans. The amount of nitrogen entering the oceans has quadrupled.

“A significant fraction of the applied nitrogen and phosphorus makes its way to the sea, and can push marine and aquatic systems across ecological thresholds of their own. One regional-scale example of this effect is the decline in the shrimp catch in the Gulf of Mexico’s ‘dead zone’ caused by fertilizer transported in rivers from the US Midwest.” – Planetary Bounderies, Stockholme Resilience Centre

Do we need a more convincing argument for going organic?

Will any of these 4 critical processes lead to the extinction of the human race?

Unless we implement radical change relatively soon, then in time, yes. Our economic system is fundamentally flawed, as it ignores these critically important life support systems. As Will Steffan puts it:

“History has shown that civilizations have risen, stuck to their core values and then collapsed because they didn’t change. That’s where we are today.”


By Jon Crooks, updated 28 April 2016